Post-mortem Bacteriological Examination on the Heart Blood of Aborted Fetuses in a Major Teaching Hospital, Shiraz, Iran, 2016 - 2017

authors:

avatar Navid Omidifar ORCID 1 , avatar Abolfazl Rafati Zomorodi ORCID 2 , 3 , avatar Mahtab Hadadi ORCID 2 , avatar Nima Hosseini 3 , avatar Mohammad Motamedifar ORCID 2 , 4 , *

Department of Pathology, Shiraz Medical School, Shiraz University of Medical Sciences, Shiraz, Iran
Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
Student Research Committee, Shiraz University of Medical Sciences, Shiraz, Iran
Shiraz HIV/AIDS Research Center, Institute of Health, Shiraz University of Medical Sciences, Shiraz, Iran
Trends in Medical Sciences: Vol.2, issue 3; e132879
published online: December 14, 2022
article type: Research Article
received: November 5, 2022
revised: November 26, 2022
accepted: November 27, 2022
DOI: https://doi.org/10.5812/tms-132879

how to cite: Omidifar N, Rafati Zomorodi A, Hadadi M, Hosseini N, Motamedifar M. Post-mortem Bacteriological Examination on the Heart Blood of Aborted Fetuses in a Major Teaching Hospital, Shiraz, Iran, 2016 - 2017. J Adv Immunopharmacol. 2022;2(3):e132879. https://doi.org/10.5812/tms-132879.

Abstract

Background:

Fetal abortion is one of the critical and controversial issues in most societies’ scientific, social, and academic ceremonies due to known and unknown reasons. Furthermore, updating our knowledge about isolated bacteria, their antibiotic resistance pattern, and related factors is essential for designing and implementing appropriate interventions.

Objectives:

The current study was conducted to determine the prevalence of bacteria among fetal abortion cases and demonstrate the antimicrobial susceptibility among isolated bacteria.

Methods:

For this, 153 blood samples were collected percutaneously from the heart blood of aborted fetuses 1 - 15 hours after birth; subsequently, the identification of bacteria and evaluation of antimicrobial susceptibility testing were performed.

Results:

Generally, 82 out of 153 test cultures were positive, comprising 66 and 26 Gram-negative and Gram-positive bacteria, respectively. The most isolated bacteria among Gram-negative isolates were Acinetobacter spp. (34/82) and Escherichia coli (17/82). Likewise, the highest antibiotic resistance was detected for Acinetobacter spp. against cefixime, amikacin, gentamycin, and ciprofloxacin (24/34). On the other hand, Staphylococcus spp. was the predominant Gram-positive cocci (10/82). Also, the highest resistance for Staphylococcus spp. was against cefoxitin and ciprofloxacin (100%).

Conclusions:

It seems more focus on following the general hygiene of pregnant mothers is essential. However, further evidence of a clinical correlation between aborted fetuses and their mothers is required.

1. Background

Fetal abortion is one of the critical and controversial issues in scientific, social, and academic contexts (1). Abortion refers to the termination of pregnancy before the 20th week or the remission of the fetus weighing less than 522 grams (2). Abortion may occur spontaneously or through induction. An abortion that occurs spontaneously is also known as a miscarriage, but induced abortion occurs when intentional measures are taken to end a pregnancy (3). For determining the reason for abortion, laboratory tests have been divided into six broad groups: genetic, anatomic, metabolic, endocrinology, immunologic, and microbiologic (4). In each of the mentioned categories, different methods are applied.

A post-mortem examination consists of a methodical examination of a corpse to find the cause, mode, and manner of death (5). Among various aspects of post-mortem examination containing pathology, histology, bacteriology, etc., post-mortem bacteriology has been applied in multiple studies, not only for distinguishing the presence of an underlying infectious disease but also for determining the cause of death (6, 7). Heart blood, cerebrospinal fluid (CSF), and spleen tissue are the most common specimens for post-mortem microbiological cultures (8). Blood culture is the most used specimen among these common specimens in various research studies. Tissue and fluid samples must be taken 1 - 15 hours after death; in this way, the possibility of post-mortem bacterial invasion will be diminished. Various species of bacteria have been mentioned to be associated with abortion, but there is no evidence of a unique organism causing abortion (5). However, we examined the bacteriological heart-blood samples of aborted fetuses to determine the bacterial profile involved in their abortion. A post-mortem exam is one of the choices that can be used as a practical examination to determine what has caused the abortion (9).

2. Objectives

Given the point of view that post-mortem bacteriologic studies can be helpful and essential to determine the reason for an abortion, the current study was conducted as the first study in Shiraz, southwest Iran, to find out the profile of the involved bacteria and their antibiotic susceptibility pattern to design and implement probable appropriate interventions.

3. Methods

3.1. Sample Collection and Study Design

This cross-sectional study was carried out from 2016 to 2017 at the medical laboratory of Hazrat Zeinab, a major referral hospital for obstetrics and gynecology teaching in Shiraz, southwest Iran. As the following description, 153 blood samples were gathered from the heart of aborted fetuses. The samples were tested as previously described by Carter (10). Briefly, a 5-cc syringe was delivered to the microbiology laboratory 1 - 15 hours after birth. Then, the blood sample was inoculated into the Tryptone soy broth (TSB) (HiMedia, India) bottle, incubated at 37°C, and examined daily for turbidity and growth. In the case of observing turbidity in the TSB bottle, after 24 h, a sub-culture was done onto the blood agar (BA) plate (HiMedia, India), chocolate agar plate (CA) (HiMedia, India), and eosin-methylene-blue agar (EMB) (HiMedia, India). If no turbidity was observed after 24 h, at intervals of 48 h, 72 h, and 10 days after the first culture subculturing in plates of BA, CA, and EMB agar was done.

3.2. Biochemical Standard Tests

Bacterial identification at the species level has been accomplished according to the biochemical standard tests as explained by Shoaib et al. (11). Briefly, the isolates have been divided regarding Gram staining results; the species of Gram-negative (GN) rod isolates were detected as illustrated in Table 1. Furthermore, Gram-positive (GP) cocci isolates have been identified as Staphylococcus spp. and Streptococcus spp. Using morphology (cluster and pairs or chains), catalase (+ and -), oxidase (- and -), and hemolysin (β and β), respectively. Eventually, the coagulase test for Staphylococcus spp. has been performed.

Table 1.

The Species-Level Identification of Gram-Negative Rod Isolates Using the Standard Biochemical Tests

Bacterial SpeciesBiochemical Tests
Gram-StainCatalaseOxidaseTSIH2SIndoleMR TestVP TestCitrateUreaseMotility
Acinetobacter spp.-+-Alk/Alk----+V-
Escherichia coli---A/A+++--+
Klebsiella spp.---Alk/A---+-+-
Enterobacter spp.---A/A---++-+
Pseudomonas spp.---Alk/Alk----+++

Abbreviations: Alk, alkaline; A, acid; TSI, triple sugar iron agar; MR, methyl red; VP, Voges Proskauer; V, variable.

3.3. Antimicrobial Susceptibility Testing

The isolated bacteria were further tested to demonstrate the antimicrobial susceptibility pattern (ASP) using the Kirby-Bauer disc diffusion method as recommended by the Clinical and Laboratory Standards Institute (CLSI, 2018) (12). The ten tried antibiotic discs were as follows: Cefoxitin (30 µg), cefixime (30 µg), cefepime (30 µg), ampicillin-Sulbactam (10/10 µg), imipenem (10 µg), gentamicin (10 µg), amikacin (30 µg), ciprofloxacin (5 µg), tetracycline (30 µg), and trimethoprim/sulfamethoxazole (1.25/23.75 µg) (Mast, UK). The Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 strains were tested for quality control.

4. Results

Out of 153 samples, 82 (53.6%) yielded positive results, among which 66 isolates (80.5%) were GN and 16 (19.5%) were GP cocci. In GN isolates, Acinetobacter spp. was the most frequent bacterium with 51.5% (34/66 isolates), and Staphylococcus spp. with a frequency of 62.5% (10/16 isolates) was the most frequent GP one. The bacterial profile of isolated strains from the heart-blood samples of septic abortion isolates is shown in Figure 1.

The frequency of isolated bacteria from heart-blood specimens (n = 82).
The frequency of isolated bacteria from heart-blood specimens (n = 82).
Figure 1.

The frequency of isolated bacteria from heart-blood specimens (n = 82).

4.1. Antimicrobial Susceptibility Testing

Generally, the highest resistance rate among GN isolates was observed against cefixime (68.2%), followed by amikacin (63.6%), gentamicin (63.6%), and ciprofloxacin (56.1%). Also, among GP isolates, the highest resistance was against ciprofloxacin (62.5%), and the most effective one was tetracycline, for which no case of resistance was detected. For Staphylococci spp., the most frequent isolate, the highest resistance rate was against ciprofloxacin and cefoxitin (100%), but all isolates were susceptible to cefepime and tetracycline. Two detected non-hemolytic Streptococci spp. were sensitive to all the tested antibiotics (Table 2).

Table 2.

The Frequency of Antimicrobial Resistance Patterns of Gram-Positive Cocci Isolated from Heart-Blood Specimens (n = 16)

Isolated Bacterial SpeciesThe Antibiotics’ Tested Name
FOXCFMFEPSAMIMPGENAMKTETCIPSXTVAN
COPS62000320641
CONS41000220420
Streptococcus spp.00000000000
Total1030005451061

Abbreviations: FOX, cefoxitin; CFM, cefixime; FEP, cefepime; SAM, ampicillin/sulbactam; IMP, imipenem; GEN, gentamicin; AMK, amikacin; TET, tetracycline; CIP, ciprofloxacin; SXT, trimethoprim/sulfamethoxazole; VAN, vancomycin; COPS, coagulase-positive Staphylococcus; CONS, coagulase-negative Staphylococcus.

Acinetobacter spp. showed a resistance pattern that the resistance rate to different antibiotics was high. As shown in Table 3 Acinetobacter spp. was resistant to amikacin, ciprofloxacin, cefixime, and gentamicin, with an equal percentage of 70.5%. Klebsiella spp. were highly (75%) resistant to amikacin, ciprofloxacin, cefixime, gentamicin, imipenem, and trimethoprim/sulfamethoxazole but entirely susceptible to tetracycline and ampicillin/sulbactam. Enterobacter spp. mainly (83.3%) resistant to amikacin, gentamicin, and cefixime but completely sensitive to cefepime and showed low resistance to tetracycline and ampicillin/sulbactam (16.6%). Isolated E. coli strains showed the most resistance rate to cefixime (64.7%), followed by amikacin and gentamicin (47%), and no resistance to cefepime and ampicillin/sulbactam.

Table 3.

The Frequency of Antimicrobial Resistance Patterns of Gram-Negative Bacteria Isolated from Heart-Blood Specimens (n = 66)

Isolated Bacterial SpeciesThe Antibiotics’ Tested Names
FOXCFMFEPSAMIMPGENAMKTETCIPSXTPMB
Acinetobacter spp.424133202424324140
Escherichia coli111004881741
Enterobacter spp.25010251320
Pseudomonas spp.01000010010
Klebsiella spp.13103330330
Total845144274242537241

Abbreviations: FOX, cefoxitin; CFM, cefixime; FEP, cefepime; SAM, ampicillin/sulbactam; IMP, imipenem; GEN, gentamicin; AMK, amikacin; TET, tetracycline; CIP, ciprofloxacin; SXT, trimethoprim/sulfamethoxazole; PMB, polymyxin B.

The other issue observed significantly among the isolated bacteria was resistance to multi-drugs. Multidrug resistance (MDR) isolates refer to those bacteria which acquire resistance to at least one agent in three or more antimicrobial groups (13). Among GN-examined isolates -besides Pseudomonas spp. -the rate of MDR was high against different antibiotic categories containing aminoglycosides (amikacin, gentamicin), fluoroquinolones (ciprofloxacin), the third generation of cephalosporin (cefixime), and beta-lactamase (imipenem). Also, among GP isolates, all Staphylococcus spp. were resistant to cefoxitin and identified as methicillin-resistance Staphylococcus, subsequently, all were considered as MDR.

5. Discussion

Abortion is a public health concern worldwide because of its mental and physical side effects, which are occasionally irreparable (14). In Iran, about 80,000 abortions occur annually (15, 16). To follow up on the influential factors in abortion, various criteria have been studied, including demographic characteristics (age, literacy, job, age of marriage, family marriage, etc.) and specific characteristics of abortion, such as the type of abortion, drinking alcohol, smoking cigarette, and drinking coffee; family history of abortion, genetic factors, and anatomic, microbiologic, endocrinologic, immunologic and metabolic factors (17, 18). Due to its significance, studies are recommended to be conducted to determine the probable reasons, focusing on preventing abortion.

Bacteria are one of the etiologic causes of abortion, and more studies are necessary to reveal the association of bacteria with abortion (19, 20). For this purpose, a post-mortem bacteriologic exam can be an optional approach. It seems that post-mortem examination is helpful for two main reasons: (1) determining the etiologic agent of an undiagnosed infection; and (2) confirming an antemortem-diagnosed infection (2, 21). The value of post-mortem bacteriology depends on a thorough autopsy, proper sampling, minimization of post-mortem bacterial translocation, and prevention of sample contamination (22). As mentioned previously, this method is ignored in most healthcare centers or done to a limited degree. Still, this examination is done routinely in a hospital in Shiraz, southwest Iran.

Generally, the frequency of isolated GN bacteria was higher than GP ones regarding the results. Among isolated bacteria, Acinetobacter spp., E. coli, and Staphylococci spp. were the most common isolates in the present study (Figure 1), which was in line with previous studies (6, 23, 24). Amongst GN isolates, Acinetobacter spp., the most isolated bacteria, is the most successful pathogen responsible for nosocomial infections in the modern healthcare system so that it can transmit and colonize quickly in individuals (25, 26). Therefore, studying the history of the mothers to find out if they have experienced hospitalization before an abortion is helpful (27). The ASP results revealed that the most effective antibiotic for GN bacteria was ampicillin/sulbactam (94%), but most isolates (66.6%) were resistant to cefixime. The resistance profile in GN isolates demonstrated notable and worrying since most were MDR; resistance to cefixime (third-generation cephalosporin) has dedicated the highest degree of resistance to itself. After Acinetobacter spp., the Klebsiella spp., Enterobacter spp., and E. coli isolates have exhibited a highly resistant rate against tested antibiotics, respectively; such resistance may be related to their intrinsic resistance mechanisms of having chromosomal and plasmid genes (28).

Among Acinetobacter spp., Acinetobacter baumannii is the most critical species related to nosocomial infections worldwide that readily become resistant to antibiotics by co-existing mechanisms and end up with MDR strains (29), as seen in the results of the current study (27, 30). Twenty out of 34 isolated strains (58.8%) yielded resistance to imipenem, which correlated with significantly increasing carbapenem resistance among A. baumannii globally associated with carbapenem-hydro-lysing enzymes (31). However, it is notable that our study could not detect to which species of Acinetobacter spp. belonged.

Among isolated GP bacteria, Staphylococcus spp. were the predominant isolates justifiable since they are found ubiquitously in nature and frequently on the skin; they are primary causative agents of various types of infection in individuals. Therefore, the mothers can be contaminated easily. Out of 10 detected Staphylococcus spp., six isolates were coagulase positive. Staphylococci spp. isolates had a high degree of resistance to ciprofloxacin, cefoxitin, amikacin, trimethoprim/sulfamethoxazole, gentamicin, and cefixime. According to cefoxitin resistance, the existence of a high frequency of methicillin-resistant Staphylococci spp. (MRSA or MRCoNS) in the present study was confirmed. Given this issue, methicillin-resistant Staphylococci is a severe concern that warrants more attention and precise management. The most effective antibiotic for Staphylococci spp. in our study was tetracycline since all the isolates were susceptible. Moreover, two Streptococcus spp. isolates have been reported as GP, both entirely susceptible to all the tested antibiotics.

The current study was limited by lacking molecular analysis; further investigation using molecular methods for determining the distribution of virulence- and antimicrobial resistance-related genes will propose more information. Also, accessing the history of the mothers of infants can improve the knowledge of the bacteriological role in abortion.

5.1. Conclusions

Most isolates were environmental bacteria with high antibiotic resistance; such bacteria might be considered causative agents of abortion in our region. Therefore, it seems more focus on following the general hygiene of pregnant mothers is essential. However, further evidence of a clinical correlation between aborted fetuses and their mothers is required.

Acknowledgements

References

  • 1.

    Fathalla MF. Safe abortion: The public health rationale. Best Pract Res Clin Obstet Gynaecol. 2020;63:2-12. [PubMed ID: 31201007]. https://doi.org/10.1016/j.bpobgyn.2019.03.010.

  • 2.

    Nigro G, Mazzocco M, Mattia E, Di Renzo GC, Carta G, Anceschi MM. Role of the infections in recurrent spontaneous abortion. J Matern Fetal Neonatal Med. 2011;24(8):983-9. [PubMed ID: 21261443]. https://doi.org/10.3109/14767058.2010.547963.

  • 3.

    Potter RG. Competition between spontaneous and induced abortion. Demography. 1975;12(1):129-41. [PubMed ID: 1112428].

  • 4.

    Coulam CB, Clark DA, Beer AE, Kutteh WH, Silver R, Kwak J, et al. Current clinical options for diagnosis and treatment of recurrent spontaneous abortion. Clinical Guidelines Recommendation Committee for Diagnosis and Treatment of Recurrent Spontaneous Abortion. Am J Reprod Immunol. 1997;38(2):57-74. [PubMed ID: 9272202]. https://doi.org/10.1111/j.1600-0897.1997.tb00277.x.

  • 5.

    Sachdeva N, Rani Y, Singh R, Murari A. Estimation of Post-Mortem interval from the changes in Vitreous Biochemistry. J Indian Acad Forensic Med. 2011;33(2):171-4.

  • 6.

    Tang RK, Liu Y, Liu YZ, Zhu SM, Huang W, Zhao P, et al. Evaluation of post-mortem heart blood culture in a Chinese population. Forensic Sci Int. 2013;231(1-3):229-33. [PubMed ID: 23890642]. https://doi.org/10.1016/j.forsciint.2013.05.020.

  • 7.

    Roberts FJ. Procurement, interpretation, and value of postmortem cultures. Eur J Clin Microbiol Infect Dis. 1998;17(12):821-7. [PubMed ID: 10052543]. https://doi.org/10.1007/s100960050200.

  • 8.

    Rambaud C, Guibert M, Briand E, Grangeot-Keros L, Coulomb-L'Herminé A, Dehan M. Microbiology in sudden infant death syndrome (SIDS) and other childhood deaths. FEMS Immunol Med Microbiol. 1999;25(1-2):59-66. [PubMed ID: 10443492]. https://doi.org/10.1111/j.1574-695X.1999.tb01327.x.

  • 9.

    Hägerstrand I, Lundberg LM. The importance of post-mortem examinations of abortions and perinatal deaths. Qual Assur Health Care. 1993;5(4):295-7. [PubMed ID: 8018885]. https://doi.org/10.1093/intqhc/5.4.295.

  • 10.

    Carter GR. Isolation and Identification of Bacteria from Clinical Specimens. In: Carter GR, Cole JR, editors. Diagnostic Procedure in Veterinary Bacteriology and Mycology. 5th ed. Massachusetts, USA: Academic Press; 1990. p. 19-39. https://doi.org/10.1016/b978-0-12-161775-2.50008-6.

  • 11.

    Shoaib M, Muzammil I, Hammad M, Bhutta ZA, Yaseen I. A Mini-Review on Commonly used Biochemical Tests for Identification of Bacteria. Int J Res Publ. 2020;54(1). https://doi.org/10.47119/ijrp100541620201224.

  • 12.

    Clinical and Laboratory Standards Institute. M100—Performance Standards for Antimicrobial Susceptibility Testing. 31st ed. Pennsylvania, USA: Clinical and Laboratory Standards Institute; 2018.

  • 13.

    Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. 31st ed. Wayne, USA: Clinical and Laboratory Standards Institute; 2011.

  • 14.

    Ortiz-Prado E, Simbaña K, Gómez L, Stewart-Ibarra AM, Scott L, Cevallos-Sierra G. Abortion, an increasing public health concern in Ecuador, a 10-year population-based analysis. Pragmat Obs Res. 2017;8:129-35. [PubMed ID: 28761387]. [PubMed Central ID: PMC5516879]. https://doi.org/10.2147/por.s129464.

  • 15.

    Rastegari A, Baneshi MR, Haji-Maghsoudi S, Nakhaee N, Eslami M, Malekafzali H, et al. Estimating the Annual Incidence of Abortions in Iran Applying a Network Scale-up Approach. Iran Red Crescent Med J. 2014;16(10). e15765. [PubMed ID: 25558379]. [PubMed Central ID: PMC4270634]. https://doi.org/10.5812/ircmj.15765.

  • 16.

    Erfani A. Abortion in Iran: What do we know? PSC Discussion Papers Series. 2008;22(1):1.

  • 17.

    Magiorakos AP, Srinivasan A, Carey RB, Carmeli Y, Falagas ME, Giske CG, et al. Multidrug-resistant, extensively drug-resistant and pandrug-resistant bacteria: an international expert proposal for interim standard definitions for acquired resistance. Clin Microbiol Infect. 2012;18(3):268-81. [PubMed ID: 21793988]. https://doi.org/10.1111/j.1469-0691.2011.03570.x.

  • 18.

    Weselak M, Arbuckle TE, Walker MC, Krewski D. The influence of the environment and other exogenous agents on spontaneous abortion risk. J Toxicol Environ Health B Crit Rev. 2008;11(3-4):221-41. [PubMed ID: 18368554]. https://doi.org/10.1080/10937400701873530.

  • 19.

    Nojomi M, Akbarian A, Ashory-Moghadam S. Burden of abortion: induced and spontaneous. Arch Iran Med. 2006;9(1):39-45. [PubMed ID: 16649376].

  • 20.

    Pandey MK, Rani R, Agrawal S. An update in recurrent spontaneous abortion. Arch Gynecol Obstet. 2005;272(2):95-108. [PubMed ID: 15906053]. https://doi.org/10.1007/s00404-004-0706-y.

  • 21.

    Donders GG, Van Bulck B, Caudron J, Londers L, Vereecken A, Spitz B. Relationship of bacterial vaginosis and mycoplasmas to the risk of spontaneous abortion. Am J Obstet Gynecol. 2000;183(2):431-7. [PubMed ID: 10942482]. https://doi.org/10.1067/mob.2000.105738.

  • 22.

    Riedel S. The value of postmortem microbiology cultures. J Clin Microbiol. 2014;52(4):1028-33. [PubMed ID: 24403308]. [PubMed Central ID: PMC3993482]. https://doi.org/10.1128/jcm.03102-13.

  • 23.

    du Moulin GC, Paterson DG. Clinical relevance of postmortem microbiologic examination: a review. Hum Pathol. 1985;16(6):539-48. [PubMed ID: 3888815]. https://doi.org/10.1016/s0046-8177(85)80102-7.

  • 24.

    Morris JA, Harrison LM, Partridge SM. Postmortem bacteriology: a re-evaluation. J Clin Pathol. 2006;59(1):1-9. [PubMed ID: 16394274]. [PubMed Central ID: PMC1860254]. https://doi.org/10.1136/jcp.2005.028183.

  • 25.

    Meshkat Z, Salimizand H, Amini Y, Mansury D, Zomorodi AR, Avestan Z, et al. Detection of efflux pump genes in multiresistant Acinetobacter baumannii ST2 in Iran. Acta Microbiol Immunol Hung. 2021;68(2):113-20. [PubMed ID: 33533731]. https://doi.org/10.1556/030.2021.01314.

  • 26.

    Oyejobi GK, Olaniyan SO, Yusuf NA, Ojewande DA, Awopetu MJ, Oyeniran GO, et al. Acinetobacter baumannii: More ways to die. Microbiol Res. 2022;261:127069. [PubMed ID: 35623161]. https://doi.org/10.1016/j.micres.2022.127069.

  • 27.

    Lee CR, Lee JH, Park M, Park KS, Bae IK, Kim YB, et al. Biology of Acinetobacter baumannii: Pathogenesis, Antibiotic Resistance Mechanisms, and Prospective Treatment Options. Front Cell Infect Microbiol. 2017;7:55. [PubMed ID: 28348979]. [PubMed Central ID: PMC5346588]. https://doi.org/10.3389/fcimb.2017.00055.

  • 28.

    G. Eyesus T, Moges F, Eshetie S, Yeshitela B, Abate E. Bacterial etiologic agents causing neonatal sepsis and associated risk factors in Gondar, Northwest Ethiopia. BMC Pediatr. 2017;17(1):137. [PubMed ID: 28587631]. [PubMed Central ID: PMC5461759]. https://doi.org/10.1186/s12887-017-0892-y.

  • 29.

    Gautam D, Dolma KG, Khandelwal B, Mitsuwan W, Mahboob T, Pereira ML, et al. Acinetobacter baumannii: An overview of emerging multidrug-resistant pathogen. Med J Malaysia. 2022;77(3):357-70. [PubMed ID: 35638493].

  • 30.

    Nowak P, Paluchowska P. Acinetobacter baumannii: biology and drug resistance - role of carbapenemases. Folia Histochem Cytobiol. 2016;54(2):61-74. [PubMed ID: 27270503]. https://doi.org/10.5603/FHC.a2016.0009.

  • 31.

    Zhang Y, Fan B, Luo Y, Tao Z, Nie Y, Wang Y, et al. Comparative analysis of carbapenemases, RND family efflux pumps and biofilm formation potential among Acinetobacter baumannii strains with different carbapenem susceptibility. BMC Infect Dis. 2021;21(1):841. [PubMed ID: 34416851]. [PubMed Central ID: PMC8377947]. https://doi.org/10.1186/s12879-021-06529-2.